#coding:utf-8
#1_10_A 2015.4.10
import math

x1,y1,x2,y2 = list(map(float,input().split()))
distance = math.sqrt((x2 - x1) ** 2 + (y2 - y1) ** 2)
print('{:.5f}'.format(distance)) import math math x1,y1,x2,y2 = list(map(float,input().split())) x1 list(map(float,input().split())) list map(float,input().split()) map float input().split() ().split () input split y1 x2 y2 distance = math.sqrt((x2 - x1) ** 2 + (y2 - y1) ** 2) distance math.sqrt((x2 - x1) ** 2 + (y2 - y1) ** 2) math.sqrt math sqrt (x2 - x1) ** 2 + (y2 - y1) ** 2 (x2 - x1) ** 2 x2 - x1 x2 x1 2 (y2 - y1) ** 2 y2 - y1 y2 y1 2 print('{:.5f}'.format(distance)) print '{:.5f}'.format(distance) '{:.5f}'.format '{:.5f}' format distance y2 = list(map(float,input().split())) list(map(float,input().split())) y2 x2,y2 = list(map(float,input().split())) list(map(float,input().split())) x2 x1,y1,x2,y2 = list(map(float,input().split())) list(map(float,input().split())) x1 y1,x2,y2 = list(map(float,input().split())) list(map(float,input().split())) y1 distance = math.sqrt((x2 - x1) ** 2 + (y2 - y1) ** 2) math.sqrt((x2 - x1) ** 2 + (y2 - y1) ** 2) distance
#coding:utf-8
#1_10_A 2015.4.10
import math

x1,y1,x2,y2 = list(map(float,input().split()))
distance = math.sqrt((x2 - x1) ** 2 + (y2 - y1) ** 2)
print('{:.5f}'.format(distance))